Painting concrete floors can be a great way to add warmth and style to a basement. Basements can be very cold and uninviting. When used for storage this is fine but if you use the area for any type of game room, or living area where people will congregate, you want the feel of the room to be a little less stark.
If you just want a nice smooth, easy to clean floor, then you also have the option of applying a concrete sealer/hardener. If you plan on finishing the basement any time in the future with ceramic tile flooring, then do not paint your floor, as the thinset mortar used for tiles will not adhere to painted surfaces., and you will be forced to strip the paint off the floor, a long dusty smelly tedious project.